SQL SERVER 查看数据库表的字段类型，是否允许为NULL，默认值，主键等

 declare @table_name   varchar(100)-- 表名
 set @table_name='bqcform101'

--============表结构
    select 类别,表名or字段名,描述,字段类型,是否自增,允许为NULL,默认值 from
    (
    SELECT '表名' 类别,-1 column_id,tbs.name 表名or字段名,ds.value 描述,'' 字段类型,'' 是否自增,'' 允许为NULL,'' 默认值,1 rn
    FROM sys.extended_properties ds
    LEFT JOIN sysobjects tbs ON ds.major_id=tbs.id
    WHERE  ds.minor_id=0 and tbs.name=@table_name
    union
    SELECT
        @table_name 类别
        ,c.column_id
        ,C.name 表名or字段名
        ,s.value 描述
        ,字段类型 = T.name + CASE T.user_type_id WHEN 41 THEN '('+CAST(C.scale AS VARCHAR) +')'     -- time
            WHEN 42 THEN '('+CAST(C.scale AS VARCHAR) +')'                                      -- datetime2
            WHEN 43 THEN '('+CAST(C.scale AS VARCHAR) +')'                                      -- datetimeoffset
            WHEN 106 THEN '('+CAST(C.precision  AS VARCHAR)+','+ CAST(C.scale AS VARCHAR) +')'  -- decimal
            WHEN 108 THEN '('+CAST(C.precision  AS VARCHAR)+','+ CAST(C.scale AS VARCHAR) +')'  -- numeric
            WHEN 165 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- varbinary
            WHEN 167 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- varchar
            WHEN 173 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- binary
            WHEN 175 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- char
            WHEN 231 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1)/2 AS VARCHAR),'MAX') +')'     -- nvarchar(该字段校检根据实际情况)
            WHEN 239 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- nchar
            ELSE ''
            END
        ,case when C.is_identity=1 then '是' else '' end 是否自增
        --cast(C.is_identity as varchar(10)) 是否自增
        ,case when C.is_nullable=1 then '是'else '' end 允许为NULL
        ,默认值 = ISNULL(STUFF(LEFT(D.definition,LEN(D.definition)-1),1,1,''),'')
        ,3 rn
    FROM sys.columns C
    INNER JOIN sys.types T ON C.user_type_id = T.user_type_id
    LEFT JOIN sys.default_constraints D ON D.[object_id] =C.default_object_id AND D.parent_object_id = C.[object_id] AND D.parent_column_id = C.column_id
    left join (select major_id,minor_id,value from sys.extended_properties) s on s.major_id = c.object_id and s.minor_id = c.column_id
    WHERE C.[object_id] = OBJECT_ID(@table_name)
    ) s
    order by column_id,rn  

--============主键
select Primary_COLUMN_NAME = convert(sysname,c.name)
from
sysindexes i, syscolumns c, sysobjects o
where o.id = object_id(@table_name)
and o.id = c.id
and o.id = i.id
and (i.status & 0x800) = 0x800
and (c.name = index_col (@table_name, i.indid,  1) or
     c.name = index_col (@table_name, i.indid,  2) or
     c.name = index_col (@table_name, i.indid,  3) or
     c.name = index_col (@table_name, i.indid,  4) or
     c.name = index_col (@table_name, i.indid,  5) or
     c.name = index_col (@table_name, i.indid,  6) or
     c.name = index_col (@table_name, i.indid,  7) or
     c.name = index_col (@table_name, i.indid,  8) or
     c.name = index_col (@table_name, i.indid,  9) or
     c.name = index_col (@table_name, i.indid, 10) or
     c.name = index_col (@table_name, i.indid, 11) or
     c.name = index_col (@table_name, i.indid, 12) or
     c.name = index_col (@table_name, i.indid, 13) or
     c.name = index_col (@table_name, i.indid, 14) or
     c.name = index_col (@table_name, i.indid, 15) or
     c.name = index_col (@table_name, i.indid, 16)
     )